 /*******************************************************************************
  * Copyright (c) 2000, 2007 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.core.internal.expressions;

 import java.util.Collection ;

 import org.w3c.dom.Element ;

 import org.eclipse.core.runtime.CoreException;
 import org.eclipse.core.runtime.IConfigurationElement;

 import org.eclipse.core.expressions.EvaluationResult;
 import org.eclipse.core.expressions.Expression;
 import org.eclipse.core.expressions.ExpressionInfo;
 import org.eclipse.core.expressions.ICountable;
 import org.eclipse.core.expressions.IEvaluationContext;


 public class CountExpression extends Expression {

     private static final int ANY_NUMBER= 5;
     private static final int EXACT= 4;
     private static final int ONE_OR_MORE= 3;
     private static final int NONE_OR_ONE= 2;
     private static final int NONE= 1;
     private static final int UNKNOWN= 0;

     /**
      * The seed for the hash code for all count expressions.
      */
     private static final int HASH_INITIAL= CountExpression.class.getName().hashCode();
     
     private int fMode;
     private int fSize;
     
     public CountExpression(IConfigurationElement configElement) {
         String size = configElement.getAttribute(ATT_VALUE);
         initializeSize(size);
     }

     public CountExpression(Element element) {
         String size = element.getAttribute(ATT_VALUE);
         initializeSize(size.length() > 0 ? size : null);
     }

     public CountExpression(String size) {
         initializeSize(size);
     }
     
     private void initializeSize(String size) {
         if (size == null)
             size= "*"; //$NON-NLS-1$
 if (size.equals("*")) //$NON-NLS-1$
 fMode= ANY_NUMBER;
         else if (size.equals("?")) //$NON-NLS-1$
 fMode= NONE_OR_ONE;
         else if (size.equals("!")) //$NON-NLS-1$
 fMode= NONE;
         else if (size.equals("+")) //$NON-NLS-1$
 fMode= ONE_OR_MORE;
         else {
             try {
                 fSize= Integer.parseInt(size);
                 fMode= EXACT;
             } catch (NumberFormatException e) {
                 fMode= UNKNOWN;
             }
         }
     }

     public EvaluationResult evaluate(IEvaluationContext context) throws CoreException {
         Object var= context.getDefaultVariable();
         int size;
         if (var instanceof Collection ) {
             size= ((Collection )var).size();
         } else {
             ICountable countable= Expressions.getAsICountable(var, this);
             if (countable == null)
                 return EvaluationResult.NOT_LOADED;
             size= countable.count();
         }
         switch (fMode) {
             case UNKNOWN:
                 return EvaluationResult.FALSE;
             case NONE:
                 return EvaluationResult.valueOf(size == 0);
             case NONE_OR_ONE:
                 return EvaluationResult.valueOf(size == 0 || size == 1);
             case ONE_OR_MORE:
                 return EvaluationResult.valueOf(size >= 1);
             case EXACT:
                 return EvaluationResult.valueOf(fSize == size);
             case ANY_NUMBER:
                 return EvaluationResult.TRUE;
         }
         return EvaluationResult.FALSE;
     }

     public void collectExpressionInfo(ExpressionInfo info) {
         info.markDefaultVariableAccessed();
     }

     public boolean equals(final Object object) {
         if (!(object instanceof CountExpression))
             return false;
         
         final CountExpression that= (CountExpression)object;
         return (this.fMode == that.fMode) && (this.fSize == that.fSize);
     }

     protected int computeHashCode() {
         return HASH_INITIAL * HASH_FACTOR + fMode
             * HASH_FACTOR + fSize;
     }
 }

